1. Technical Field
Embodiments described herein generally relate to processors. In particular, embodiments described herein generally relate to loading data from memory in processors.
2. Background Information
The instruction set of a processor typically includes a variety of different types of instructions that the processor is able to execute or perform. For example, commonly the instruction set may include various arithmetic instructions, various logical instructions, various load instructions to load data from memory into the processor, etc.
One challenge is that the number of instructions that may be included in the instruction set is generally limited. Each of the instructions may include an operation code or opcode. The opcodes may represent portions of the instructions that are used to specify the particular instructions and/or operations to be performed. For example, a given data load from memory instruction may have a given unique opcode to distinguish it from other types of instructions and allow the processor to recognize it. The opcode may represent a group of bits of a given length in one or more fields or locations within the instruction format. Often, it is desirable to try to keep the number of bits of the opcodes relatively short, while providing the desired number of instructions/operations. Long opcodes tend to increase the size and/or complexity of the decoder. In addition, long opcodes tend to increase overall instruction length, which may cause the instructions to use more program space and take up more space in caches. The number of different instructions that can be uniquely identified with a given opcode length and/or instruction length is often more limited than desirable. Additional instructions typically cannot be continually added to the instruction set without ultimately running out of available opcodes or increasing the length of the instructions in variable instruction length architectures.
In some cases, different instructions and/or operations may have the same opcode (or same portion of the opcode) but may include one or more additional bits to differentiate between different versions of the instruction and/or operation. Potential drawbacks to this approach is that it may tend to increase the instruction length, or in some cases there may not be available room within the instruction length to accommodate the additional bit(s) to distinguish between the different versions of the instruction/operation